1 // Copyright 2010 Google Inc. All Rights Reserved.
2 //
3 // This code is licensed under the same terms as WebM:
4 // Software License Agreement: http://www.webmproject.org/license/software/
5 // Additional IP Rights Grant: http://www.webmproject.org/license/additional/
6 // -----------------------------------------------------------------------------
7 //
8 // Low-level API for VP8 decoder
9 //
10 // Author: Skal (pascal.massimino@gmail.com)
11
12 #ifndef WEBP_WEBP_DECODE_VP8_H_
13 #define WEBP_WEBP_DECODE_VP8_H_
14
15 #include "webp/decode.h"
16
17 #if defined(__cplusplus) || defined(c_plusplus)
18 extern "C" {
19 #endif
20
21 //------------------------------------------------------------------------------
22 // Lower-level API
23 //
24 // These functions provide fine-grained control of the decoding process.
25 // The call flow should resemble:
26 //
27 // VP8Io io;
28 // VP8InitIo(&io);
29 // io.data = data;
30 // io.data_size = size;
31 // /* customize io's functions (setup()/put()/teardown()) if needed. */
32 //
33 // VP8Decoder* dec = VP8New();
34 // bool ok = VP8Decode(dec);
35 // if (!ok) printf("Error: %s\n", VP8StatusMessage(dec));
36 // VP8Delete(dec);
37 // return ok;
38
39 // Input / Output
40 typedef struct VP8Io VP8Io;
41 typedef int (*VP8IoPutHook)(const VP8Io* io);
42 typedef int (*VP8IoSetupHook)(VP8Io* io);
43 typedef void (*VP8IoTeardownHook)(const VP8Io* io);
44
45 struct VP8Io {
46 // set by VP8GetHeaders()
47 int width, height; // picture dimensions, in pixels (invariable).
48 // These are the original, uncropped dimensions.
49 // The actual area passed to put() is stored
50 // in mb_w / mb_h fields.
51
52 // set before calling put()
53 int mb_y; // position of the current rows (in pixels)
54 int mb_w; // number of columns in the sample
55 int mb_h; // number of rows in the sample
56 const uint8_t* y, *u, *v; // rows to copy (in yuv420 format)
57 int y_stride; // row stride for luma
58 int uv_stride; // row stride for chroma
59
60 void* opaque; // user data
61
62 // called when fresh samples are available. Currently, samples are in
63 // YUV420 format, and can be up to width x 24 in size (depending on the
64 // in-loop filtering level, e.g.). Should return false in case of error
65 // or abort request. The actual size of the area to update is mb_w x mb_h
66 // in size, taking cropping into account.
67 VP8IoPutHook put;
68
69 // called just before starting to decode the blocks.
70 // Must return false in case of setup error, true otherwise. If false is
71 // returned, teardown() will NOT be called. But if the setup succeeded
72 // and true is returned, then teardown() will always be called afterward.
73 VP8IoSetupHook setup;
74
75 // Called just after block decoding is finished (or when an error occurred
76 // during put()). Is NOT called if setup() failed.
77 VP8IoTeardownHook teardown;
78
79 // this is a recommendation for the user-side yuv->rgb converter. This flag
80 // is set when calling setup() hook and can be overwritten by it. It then
81 // can be taken into consideration during the put() method.
82 int fancy_upsampling;
83
84 // Input buffer.
85 size_t data_size;
86 const uint8_t* data;
87
88 // If true, in-loop filtering will not be performed even if present in the
89 // bitstream. Switching off filtering may speed up decoding at the expense
90 // of more visible blocking. Note that output will also be non-compliant
91 // with the VP8 specifications.
92 int bypass_filtering;
93
94 // Cropping parameters.
95 int use_cropping;
96 int crop_left, crop_right, crop_top, crop_bottom;
97
98 // Scaling parameters.
99 int use_scaling;
100 int scaled_width, scaled_height;
101
102 // If non NULL, pointer to the alpha data (if present) corresponding to the
103 // start of the current row (That is: it is pre-offset by mb_y and takes
104 // cropping into account).
105 const uint8_t* a;
106 };
107
108 // Internal, version-checked, entry point
109 int VP8InitIoInternal(VP8Io* const, int);
110
111 // Set the custom IO function pointers and user-data. The setter for IO hooks
112 // should be called before initiating incremental decoding. Returns true if
113 // WebPIDecoder object is successfully modified, false otherwise.
114 int WebPISetIOHooks(WebPIDecoder* const idec,
115 VP8IoPutHook put,
116 VP8IoSetupHook setup,
117 VP8IoTeardownHook teardown,
118 void* user_data);
119
120 // Main decoding object. This is an opaque structure.
121 typedef struct VP8Decoder VP8Decoder;
122
123 // Create a new decoder object.
124 VP8Decoder* VP8New(void);
125
126 // Must be called to make sure 'io' is initialized properly.
127 // Returns false in case of version mismatch. Upon such failure, no other
128 // decoding function should be called (VP8Decode, VP8GetHeaders, ...)
VP8InitIo(VP8Io * const io)129 static WEBP_INLINE int VP8InitIo(VP8Io* const io) {
130 return VP8InitIoInternal(io, WEBP_DECODER_ABI_VERSION);
131 }
132
133 // Start decoding a new picture. Returns true if ok.
134 int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io);
135
136 // Decode a picture. Will call VP8GetHeaders() if it wasn't done already.
137 // Returns false in case of error.
138 int VP8Decode(VP8Decoder* const dec, VP8Io* const io);
139
140 // Return current status of the decoder:
141 VP8StatusCode VP8Status(VP8Decoder* const dec);
142
143 // return readable string corresponding to the last status.
144 const char* VP8StatusMessage(VP8Decoder* const dec);
145
146 // Resets the decoder in its initial state, reclaiming memory.
147 // Not a mandatory call between calls to VP8Decode().
148 void VP8Clear(VP8Decoder* const dec);
149
150 // Destroy the decoder object.
151 void VP8Delete(VP8Decoder* const dec);
152
153 //------------------------------------------------------------------------------
154 // Miscellaneous VP8/VP8L bitstream probing functions.
155
156 // Returns true if the next 3 bytes in data contain the VP8 signature.
157 WEBP_EXTERN(int) VP8CheckSignature(const uint8_t* const data, size_t data_size);
158
159 // Validates the VP8 data-header and retrieves basic header information viz
160 // width and height. Returns 0 in case of formatting error. *width/*height
161 // can be passed NULL.
162 WEBP_EXTERN(int) VP8GetInfo(
163 const uint8_t* data,
164 size_t data_size, // data available so far
165 size_t chunk_size, // total data size expected in the chunk
166 int* const width, int* const height);
167
168 // Returns true if the next byte(s) in data is a VP8L signature.
169 WEBP_EXTERN(int) VP8LCheckSignature(const uint8_t* const data, size_t size);
170
171 // Validates the VP8L data-header and retrieves basic header information viz
172 // width, height and alpha. Returns 0 in case of formatting error.
173 // width/height/has_alpha can be passed NULL.
174 WEBP_EXTERN(int) VP8LGetInfo(
175 const uint8_t* data, size_t data_size, // data available so far
176 int* const width, int* const height, int* const has_alpha);
177
178 #if defined(__cplusplus) || defined(c_plusplus)
179 } // extern "C"
180 #endif
181
182 #endif /* WEBP_WEBP_DECODE_VP8_H_ */
183